1. Field of the Invention
The present invention is generally directed to the field of tool joints, and, more particularly, to a shoulder refacing indicator, and methods of using same.
2. Description of the Related Art
A string of oil and gas well drill pipe is made up of sections of pipe, each about 30 feet long. Each section has an externally threaded pin on one end and an internally threaded box on the other end. When coupled together, the pin and the box form a tool joint. Each set of threads is tapered and has a point where the pitch diameter is a specific amount, this point being known as the gage point. A make-up shoulder is spaced a selected distance from the gage point of the threads on the pin. Another make-up shoulder is located at the outer end of the box. When fully made-up, these make-up shoulders contact each other under a selected amount of compression to provide a fluid-tight seal. To achieve the proper amount of compression, the distance from the pin make-up shoulder to the gage point of the pin threads, and the distance from the box make-up shoulder to the gage point of the box threads, must be carefully controlled.
During use, the make-up shoulders may gall and score. To achieve a smooth surface again, the shoulders are redressed. It is important that the total material removed from the two mating shoulders may be no more than 1/16 inch from original, or no more than 1/32 inch from any shoulder. If the material removal totals more than 1/16 inch from mating shoulders, inadequate compression may occur during make-up, thus requiring the mating faces to be remachined. Without such corrective measures, fatigue failures and washouts may result.
U.S. Pat. No. 4,438,953 (“the '953 patent”) discloses a benchmark consisting of a benchmark shoulder formed around the pin outer diameter ⅛ inch from the make-up shoulder. The box counterbore had a step formed around it ⅛ inch from the make-up shoulder. The benchmark shoulder provides a reference line to determine the distance from the make-up shoulder to the reference line, after the make-up shoulder had been redressed. Because the benchmark is a continuous step around the circumference of the pin outer diameter, and a continuous counterbore around the circumference of the box inner diameter, it also serves as an indicator of uneven machining of the tool joint shoulder. The benchmark in the '953 patent is placed on the tool joint during the operation in which threads are machined onto the tool joint.
The benchmark shown and described in the '953 patent has proven to be successful, but suffers from a drawback in that, when the joint has been made up, the benchmark can neither be seen nor measured. In order to determine if the maximum amount of facing has been performed on the mating shoulder surfaces, the joint must be uncoupled, and a measurement made to make this determination. Also, certain prior art benchmarks require the removal of a thread protector, and a certain amount of cleaning of the connection itself prior to making a determination as to whether or not the faces must be machined.
U.S. Pat. No. 6,896,300 (“the '300 patent”), which is assigned to the assignee of the present application, describes a tool joint in which a refacing benchmark is formed on the external bevel on the tool joint connection. The refacing benchmark shows the position of the original shoulder so an inspector can estimate the amount of refacing a connection has undergone and determine if excessive refacing has occurred. Although the invention described in the '300 patent provides significant improvement relative to the prior art, a need still exists for a device that allows for a very quick and very accurate determination as to whether or not a tool joint may be refaced.
The present invention is directed to devices and methods that may solve, or at least reduce, some or all of the aforementioned problems.